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    <title>Document</title>
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    <script>
        //实例化Promise对象
        const p = new Promise(function (resolve, reject) {
            setTimeout(function () {
                //
                // let data = '数据库中的用户数据'
                // resolve(data);
                let err = '数据读取失败'
                reject(err)
            }, 2000)

        });

        //调用promise对象的then方法
        //成功调用这个
        p.then(function (value) {
            console.log(value);

            //失败调用这个
        }, function (reason) {
            console.log(reason);
        })
    </script>
</body>

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